The purpose of the proposed project is to identify the efferent projections of the accessory optic nuclei. The efferent projections of these nuclei (the dorsal accessory optic nucleus, and the medial accessory optic nucleus) will be determined by two complementary methods. One method will employ anterograde degeneration techniques following punctate lesions of each nucleus. This method will be used to trace the course and the termination of the pathways arising from each of the accessory optic nuclei. The other method will employ autoradiography following intranuclear injections of tritiated proline. This will permit the tracing of labeled proteins which will be transported from accessory optic nuclei to points of termination in the brainstem. It is hoped that this study will clarify the relationship of the accessory optic nuclei to the visual system and also lead to functional inferences that can be tested behaviorally.